1. Field of the Invention
The invention relates to a projector and more particularly to a projector with polarized light recycling system for improving the use efficiency of polarized light.
2. Description of the Related Art
In some kinds of projectors, for example an LCOS projector, the optical engine includes a liquid crystal panel which can only use linear polarized light. In these kinds of projectors, therefore, unpolarized light generated by the light source module is converted into linear polarized light for the utilizing of the liquid crystal panel. However, about a half of light energy is lost when unpolarized light is converted into linear polarized light, and only a half of light energy (linear polarized light) can be utilized by the liquid crystal panel. In order to convert more unpolarized light into linear polarized light for the utilizing of the liquid crystal panel, a polarization conversion system is developed to convert the useless light into useful linear polarized light for the liquid crystal panel.
As shown in FIG. 1, a well-known polarization conversion system 10 includes a number of strip-shaped polarization beam splitters 102 and retarders 103. When unpolarized light U101 is directed toward the polarization conversion system 10, fifty percent of the unpolarized light U101, represented by the first S-polarized light S104, is reflected by polarization beam splitter 102 and the other fifty percent of the unpolarized light U101, represented by the first P-polarized light P105, passes through the polarization beam splitter 102. The reflected first S-polarized light S104 is reflected once more and leaves the polarization conversion system 10. The first P-polarized light P105 continues to pass through the retarder 103, wherein the most part of it is converted to the second S-polarized light S106 and a little part of it is not converted that is represented by the second P-polarized light P107. Thus, the polarization conversion system 10 converts useless linear polarized light P105 into useful linear polarized light S106. The well-known polarization conversion system 10 effectively increases the polarized light conversion efficiency of light source, but there is still little energy of linear polarized light P107 cannot be converted into useful linear polarized light.